Discharge tube



' Patented Feb. 18, 1936 UNITED STATES,

mscnAneE TUBE Claude, Nanterre, France, assignor to Socie't Anonyme pourles Applicationsde lElectricit et des Gaz Bares EtablissementsClaude-Paz & Silva, Paris, France, a corporation of France No Drawing.Application April 8, 1934, Serial No.

718,885. In France April 8, 1933 8 Claims. (01. 176-122) It has alreadybeen proposed to modify the light emitted from electric discharge tubesor ,receptacles. In one process, the glass envelope is constituted bycolored or fluorescent substances, or is covered by them. It has alsobeen proposed to produce a kind of light specially chosen, for example asky-blue effect, by the application or use of a filter in conjunctionwith a mercury discharge lamp, or to fit up a double walled receptaclefor the like purpose. It has also been proposed to mount a luminous.discharge tube in a recess, the interior of which is coated with asuitable phosphorescent or other lining, or again, to provide an axialpartition extending the whole length of the interior of the electricdischarge tube: and having on at least one side a coating of afluorescent substance, for example zinc sulphide, oxide-of scandium, orcalcium tungstate, orentirely composed of a fluorescent 20 material.Coatings of gold or silver have also been proposed with, as fillingmaterials, sodium,

cadmium or mercury. There has been suggested a combination ofincandescent lamps and discharge tubes constituting table lamps,standard lamps, and hanging or ceiling lamps; arranged with the hotelectrodes, heating, igniting and stabilizing apparatus'in the feet orthe handlesof the saidlamps. Finally, it has been suggested to apply ahomogeneous and adhesive coating to the interior of electric dischargetubes by spraying luminous paint over a binder of low surface tensionand high viscosity, as for example a polyvalent alcohol such'asglycerine, and to remove the binder or adhesive by means of heat orvacuum or both of these; it has also been proposed to add to theadhesive to be volatilized,

compounds of metalloid elements such as boric acid, borax or other boroncompounds, or sodium silicate.

As far as applicant knows, no tube provided with an internal luminouscoating has yet been manufactured commercially.

An object of the present invention, is to provide electric dischargetubes and receptacles for as the adhesive must not be in excess and thatthis 'commercial'use, the interior of which is coated- Bass adhesive orbinder will only have the desired effect when it is. applied in the formof an extremely thin and homogeneous film, and that, finally; in orderto. avoid undesirable deposits of metallicvapors, the additionof themercury or any other metal must. be carefully measured according to theparticular conditions applicabl It is also. necessary to take care toensure the ceptacles by preventing as far as possible any satisfactoryconstruction of the discharge rediffusion of hydrocarbon vapors on thefinal sealing-in after the evacuation and filling'up with 4 neon or anyother gas or vapor.

. A further advantage of the present invention consists in that, by asuitable selection of colorlessor colored glass constituting thedischarge.

receptacle, in combination with the luminous coating which it is desiredto apply,,it is possible to produce color effects which hitherto it hasbeen impossible to. obtain. For example, by using a tube of green glassand the known'mixtur'e of' mercury, neon, argonand helium, as the conductive gas of the luminescent discharge, and by coating the inside of thetube, in accordance with -'the invention, with a luminous material suchas a mixture of zinc sulphide and cadmium sulphide, there is obtained ayellow color, whereas hitherto j the known dischargewas of a greencolor.

Evidently a large variety of luminous effects thus become possible byvarying the .glass, the filling gas, and the internal luminous material;

'In carying' out the present invention, whether the glass used iscolorless or colored, and, whatever may be the filling gas or theinternal luminous coating, it is possible to construct novel dischargetubes or receptacles provided with the internal luminous coating, and inwhich the electric contactis established-by means of suitable terminalscapable of insertion in, a handle or hollow support equipped withcorresponding conor other auxiliary apparatus for the ignition ormaintenance of the discharge in the tube.

It is also necessary to prevent the production of unusual reactionswhich would counteract the effect of. the luminous coating or whichwould tend to diminish the adhesion of the luminous substance tothefinnersurface' of the glass, or

which would form deposits adapted to soil the discharge tubes. To betterunderstand the. man- 45, tacts, containing when necessary thetransformer ufacture of the tubes according to the presentinvention,there will be given the following special particulars, it beingunderstood that they do not restrict the scope of the invention.

A colorless or colored tube is given the final shape desired,'forexample that of a circle or-any other shape; it is carefully freed fromall fatty or like matter by the known process of washing withalcohol andthen drying with ether. By

means of a string passed through the tube, as is done for glass beads,there ispassed through the tube a plug of fabric or a sponge which hasbeen impregnated to the desired extent with a temporary binder; forexample glycerine containing boric acid in solution. This process hashowever the disadvantage of causing irregularities and interruptions inthe deposit of the liquid containing the luminescent substances;furthermore,

it often happens and especially when the electric discharge apparatushas curves, or pronounced bends, that the string or the tube breaks.These v disadvantages may be avoided by producing the movement of theimpregnated body by the effect of a regulated force. In the elbows inparticular the force should be greater than in the straight parts. Themovement of the body may be obtained by means of the pressure of thegas,the said pressure being regulated for example by means of a two-waycock. on passing elbows. the pressure will be increased progressiveland, when the body has passed the elbow, the pressure will be brought toits initial value. This pressure the other face may be obtained.

. The displacement of the impregnated, body in the discharge apparatusmay also be effected by the action of a magnetic field on one or moremagneticmasses connected to the said impregnated body. This magneticfield may be adjustable-so as to be increased with agview to themovement of the "body in the bent part of the tube.

sive, the plug is passed along in the opposite direc- As regards thecharacter of the adhesive, applicant has found that the mixture of onepart of boric acid and of five parts-of anhydrous glycerine is very.suitable for the operation. In order to ensure the homogeneity; of thetemporary adhetion, the operation being repeated, using, if desired,decreasing quantities of glycerine or similar products. ,To complete theuniform application of the glycerine or the like, it is'even essentialin order to remove any excess beyond the quantity necessary toconstitute a very thin and homogeneous film, to pass through. the tube adry plug or sponge and torepe'at the operation in the reyerse directionto remove as far as possible any trace of glycerine or the like, visibleoncareful examination. Ony then is the luminescent substance introducedinto the tube. This is effected by shaking the tube, rfwhich there is anexcess for example of sulphide of zinc, containing the ingredientsnecessary for producing the luminescence and withdrawing by shaking orother means any material not adhering to the film of glycerine. or likeproduct; itshouldbe pointed 2,oso,oos V out in this conn'ection that anyaccumulation of glycerine or similar product in the bends would cause adiminution of luminosity.

After the luminous coating has been applied on to the internal surfaceof the tube, the temporary adhesive is removed by heating. when themixture of glycerine and boric acid has been used, the inventors havefound that it is advis- .able to heat the tube slightly above theboiling point of the glycerine, and to maintain a temperature of 330 to350 C. for about twenty to thirty minutes. 1

The heating is stopped when the temperature of 350C. is reached, and thetubes are allowed to slowly cool. The electrodes are then inserted andsealed; 1 the sealing must be carried out in such manner as to preventany diffusion of hydrocarbon gases into the discharge tube. Ifconsidered necessary, a spirit flame may be used to this end.After'this, the tubes are ready for the vacuum to be created, and thisis obtained by the known process, taking care to free the electrodesfrom any occluded gas, by heatin by means of high potential or the like,and also reducing the temperature to the limit which will not causedeterioration'of the luminous substance. In general, a temperature of350 C. approximately is necessary and has given satisfactory results. 1

Before sealing the tube, one or more rare gases from the air areintroduced at a low pressure and, if desired, a small quantity of metal,such as mercury, taking care to avoid any excess of the said metalbeyond that which is actually necessary.

The discharge receptacle or tube is now ready for insertion in thecontact pieces of a support, handle or other. similar apparatus which,for

greater conveniencewill be hollow and in which the supply terminals, thetransformer-if necessaryand another auxiliary apparatus required for theignition and the stabilization of the discharge will be fitted.

I claim:

1. The method of manufacturing gas filled electric luminous dischargetubes and the like having. their inner surface provided, by theintermediary of a. volatilizable cementing agent, with a layer ofluminescent or phosphorescent substance, comprising applying the.cementing agent in an extremely thin andsuniform layer on said surfaceby wiping with a plug of elastic absorbent material impregnated with thecementing agent, depositing the luminescent or phosphorescent substancein a thin film on the wiped surface. and eliminating the cementingagent.

2. The method of manufacturing gas filled electric luminousdischargetubes and the like having their inner surface provided, by theintermediary of a volatilizable cementing agent, with a layer ofluminescent or phosphorescent substance, comprising applying thecementing agent in an extremely thin and uniform layer on said surfaceby wiping with a plug ,of elastic absorbent material impregnatedwithlthe cementingagent, attenuatingthe layer of cementing agent bywiping with a plug of dry elastic material, depositing the luminescentor phosphorescent substance in a thin mm on the wiped surface. andeliminatplug is moved 5. A method according to claim 1 in which the plugis moved through the tube by means of a magnetic field operative upon amagnetic body embedded in the plug.

6. A method according to claim 1 in which the luminescent substance isintroduced along with and in solution in the cementing agent.

7. The method of manufacturing gas filled electric luminous dischargetubes and the like having their inner surface provided, by theintermedian of a volatilizable cementing agent, with depositing theluminescent or phosphorescent,

substance in a thin film on the wiped surface, and sealing theelectrodes in the tube with avoidance of diflfusion of hydrocarbons intothe tube.

8. A method according to claim 7 in which the electrodes are scaled intothe tube with the aid of a spirit flame.

